Ornis Fennica 85:73–81. 2008

Scandinavian and central European subspecies of White-throated Dipper Cinclus cinclus interbreed in an isolated population in northern Poland

Arkadiusz Sikora & Grzegorz Neubauer

A. Sikora, Ornithological Station, Museum and Institute of Zoology, Polish Academy of Sciences, Nadwiœlañska 108, 80-680 Gdañsk, Poland. [email protected] G. Neubauer, corresponding author: Grzegorz Neubauer, Ornithological Station, Mu- seum and Institute of Zoology, Polish Academy of Sciences, Nadwiœlañska 108, 80-680 Gdañsk, Poland. [email protected]

Received 12 January 2008, revised 27 February 2008, accepted 15 April 2008

Breeding ranges of Scandinavian and central European subspecies of the White-throated Dipper (Cinclus cinclus cinclus and C. c. aquaticus)are geographically separated by un- inhabited lowlands. Between 1990 and 2006, 25 confirmed and 4 probable breeding cases of 23 individual dipper pairs were recorded in northern Poland. Dippers breeding in Northern Poland represented the Scandinavian cinclus phenotype in most cases (76% of males and 89% of females), while a minority phenotypically resembled the Carpathian aquaticus (24% and 12%, respectively). Offspring of a phenotypically mixed pair – two males from the same brood – displayed an intermediate phenotype. Ringing recoveries confirmed that immigrants from both ranges breed in N Poland. In 15 out of 23 breeding pairs, both mates represented the cinclus phenotype, one breeding attempt was by a pure aquaticus pair, and interbreeding pairs (cinclus × aquaticus)occurred in 7 out of 23 cases. Most breeding attempts were successful, and pair composition had only little if any effect on breeding success. A single individual hatched in Northern Poland was subsequently found breeding in Sweden. Out-of-range populations, such as the studied Northern Polish one supported by individuals from allopatric ranges, may promote the gene flow between allopatric subpopulations, contributing to the high morphological variability and the re- ported low genetic differentiation between the two studied subspecies.

1. Introduction restricted to high mountains (Tyler & Ormerod 1994). In Europe, C. c. cinclus (hereafter referred The polytypic genus Cinclus consists of five spe- to as cinclus)breeds in Scandinavia, and exhibits cies distributed in Eurasia and the New World (Ty- migratory habits with regular south-west, south, ler & Ormerod 1994). In the Western Palaearctic, and south-east wintertime movements up to a few the only breeding species is the White-throated hundred km (Andersson & Wester 1976, Lehikoi- Dipper Cinclus cinclus with2to17formallyrec- nen & Hakala 1988, Sikora 1993, Vuorinen & ognized subspecies (Ormerod & Tyler 2005). Tyrberg 1994). Central European subspecies C. c. White-throated Dipper has a patchy distribution, aquaticus (hereafter referred to as aquaticus)is a 74 ORNIS FENNICA Vol. 85, 2008 short-distance or vertical migrant (Zink 1981, corroborate the origin of Northern Polish breeders. Glutz & Bauer 1985). The winter range of Scandi- Furthermore, because reproductive barriers be- navian cinclus nearly overlaps with the breeding tween subspecies are unlikely due to the similar range of aquaticus in the German Lowland, yet in- ecological requirements and low genetic diver- terbreeding is unconfirmed despite a few sug- gence, we predicted that (2)if some aquaticus im- gested cases (Creutz 1986, Bink 1992). migrants would occur, they would mate and suc- Morphologically, the coloration of head, hind cessfully reproduce with cinclus, thus confirming neck and breast are reddish brown in aquaticus interbreeding between the two subspecies. By val- and blackish brown in cinclus. Dippers from Cen- idating these two hypotheses, we aimed at clarify- tral Europe are also smaller and tend to have paler ing whether such an out-of-range population could legs than do Scandinavian dippers (Cramp 1988, act as a bridge between allopatric populations, pro- Tyler & Ormerod 1994). There is no indication of moting gene flow and contributing to the low ge- genetic differentiation between these subspecies, netic differentiation between subspecies of the and other European subspecies also show little dif- White-throated Dipper in Europe. ferentiation that could be reasonably linked to their geographic distribution (Lauga et al. 2005). White-throated Dippers of cinclus type have also 2. Methods been assigned to areas of central France, north- western Spain, Corsica and Sardinia (Niethammer We conducted field surveys in Pomeranian and 1965). However, despite the fact that the breeding Masurian Lakelands, Northern Poland (53°30’N– ranges of aquaticus and cinclus-like birds largely 54°50’N, 16°50’E–20°40’E; Fig. 1). These dis- overlap in Spain (Campos et al. 2005a), no evi- tricts consist of moraine hills, reaching up to 329 m dence for interbreeding has been reported. The oc- a.s.l., which create a diverse relief with relative currence of dark, cinclus-like individuals within heights up to 100 m (Kondracki 2002). Field sur- Central European populations of aquaticus still veys were carried-out on 1,400 km of fast-flowing lacks an explanation. Either they originate from streams and rivers with a gradient in excess of 1‰. Fennoscandian birds that migrate to Central Eu- Using distribution data of wintering White- rope to overwinter there, or they represent aberrant throated Dippers during the preceding winter individuals within aquaticus subspecies (von (Sikora 1993)and their behaviour (e.g., displaying Burg 1924, Greenway & Vaurie 1958, Balat 1961, pair, singing individual, or birds with nest mate- Spitznagel 1995a, 1995b). rial), we explored selected rivers to search for Breeding habitat for White-throated Dippers is breeding pairs in March–June, between 1990 and scarce between the mountain ranges of Central Eu- 2006. Where possible, we collected data on breed- rope (breeding range of aquaticus)and Scandina - ing success. via (breeding range of cinclus). Therefore, low- We measured birds from the subspecies lands of Central Europe are only exceptionally in- cinclus and aquaticus. We obtained morphologi- habited. In the early 1990’s, an isolated population cal data on cinclus (n = 49; 21 females and 28 of dippers, consisting of 1–5 breeding pairs, was males)from birds wintering in Northern Poland, discovered in Northern Poland. This area is a regu- between 1993 and 2003. We used only individuals lar winter range of Scandinavian cinclus (Sikora for which ringing recoveries had confirmed their 1993). Alternatively, aquaticus is solely a short- Scandinavian origin; they had thus been recorded distance migrant; hence, we predicted that (1) within cinclus breeding range in Scandinavia Northern Poland would be mostly inhabited by in- (58°20’N–64°50’N, 06°00’E–15°20’E; Fig. 1). dividuals originating from Scandinavia rather than Breeding in Scandinavia was confirmed for 29 of from Central Europe. We evaluated this hypothe- these birds, whereas the remaining 20 individuals sis by comparing the phenotypic characteristics of had also been recorded within the breeding range birds from Scandinavia, Carpathians and Northern of cinclus, though not during breeding season (not Poland. Due to the high within-population mor- mapped); all these individuals are considered to phological variability of the species, we also used represent cinclus. information obtained from ringing recoveries to We trapped specimens of aquaticus (n = 27; 16 Sikora & Neubauer: White-throated Dipper interbreeding in Poland 75

Fig. 1. The distribution of the White-throated Dipper popu- lations (shaded sections; up- dated from Hagemeijer & Blair 1997), and the study ar- eas (boxes; Northern Poland [N POLAND] and the Carpa- thians [CAR]). Breeding lo- calities in Northern Poland are shown as open circles for pairs with both birds display- ing cinclus phenotype, down- triangles for phenotypically mixed pairs, and up-triangles for pairs with both birds dis- playing aquaticus phenotype. Black squares in Scandinavia indicate breeding localities of birds used as a reference po- pulation of cinclus; arrows join ringing and breeding lo- cations. females and 11 males)in Beskid Niski mountain was incubating eggs and feeding young at the nest. range, South-Eastern Poland (49°20’N–49°40’N, Subspecific identification of two other individuals 21°00’E–21°50’E; Fig. 1)in September 2002. Be - was based on visual observations in their breeding cause this subspecies is a short-distance or vertical territories. Based on classic subspecific features, migrant, we consider these individuals to represent these two individuals could safely be identified as a local population of aquaticus. cinclus-like. Two White-throated Dippers, ringed We also mist-netted, ringed and measured as nestlings in Northern Poland, were re-trapped adult White-throated Dippers breeding in an out- as adults. of-range population in Northern Poland (n = 34; We measured the trapped dippers according to 18 females and 16 males). Between 1990 and Svensson (1992): wing length (maximum flat- 1999, we marked dippers using unique combina- tened chord), tarsus length, total head length, bill tions of color rings, allowing for individual identi- length (feathering to tip)and bill depth at the distal fication during the subsequent seasons. For each edge of nostrils. Additionally, we measured bill individual, we ascertained its breeding status. We length to distal edge of nostrils. All measurements trapped 34 and visually identified two individuals, were taken by the author A. S. to the nearest 0.1 making up a total of 23 breeding pairs (four males mm. We weighted birds to the nearest g. We also and two females were involved in more than one evaluated three color-based variables under ambi- breeding pair); a single breeding male remained ent light conditions: (1)the amount of reddish- unidentified as it was not recorded when its female brown feathers on the breast, classified using a 76 ORNIS FENNICA Vol. 85, 2008 four-step scale (0%, 1–30%, 31–60%, >60%), (2) Table 1. Repeatability of measurements of 48 the color of the head and hind neck, classified us- White-throated Dippers in Northern Poland. ing a three-step scale (dark brown, intermediate, brown)and (3)the leg color, classified using a Measure- Repea- F df P ment tability three-step scale (dark, intermediate, pale). These three categorical variables were polarized so that Wing length 0.99 232.86 47; 113 <0.0001 high scores corresponded to aquaticus and low Head length 0.90 31.95 45; 105 <0.0001 scores to cinclus. Bill length 0.79 13.82 47; 113 <0.0001 In Northern Poland, birds showing cinclus col- Bill: from tip oration were initially sexed by wing length to nostrils 0.80 14.47 47; 109 <0.0001 Bill depth 0.81 15.28 47; 112 <0.0001 (Svensson 1992). Individuals with aquaticus-like Tarsus 0.94 54.51 47; 113 <0.0001 coloration were sexed according to Bub (1984) and to Schmid and Spitznagel (1985): birds with wing length less than 92 mm were considered fe- males, and larger ones males. Because body mass Principal Component Analysis (PCA)using a cor - appears to be a good predictor of sex (Esteban et relation matrix on the morphological data of 112 al. 2000, Campos et al. 2005b), we also plotted White-throated Dippers (55 females, 55 males, body mass against wing length. By obtaining two and two males ringed as nestlings in the nest of a nearly discrete groups of points we confirmed that phenotypically mixed pair). Prior to the analysis, a combination of wing length and body mass al- we log-transformed continuous variables to ap- lows reliable sexing of individuals. According to proach normal distributions and ranked the dis- the equation of Esteban et al. (2000), crete variables (Siegel & Castellan 1988). Sexes were analyzed separately to emphasize differences Y = body weight + (2 × wing length in mm)= 243 (1) between subspecies rather than between sexes. In univariate comparisons we used Student’s t test individuals with Y > 243 are considered males and (Sokal & Rohlf 1995). We carried out the statisti- those with Y < 243 females. Of the 243 studied cal analyses using SPSS 15.0. Northern Polish breeding females, three were The phenotypic assignment of Northern Polish misclassified and one was unclassified when this breeders was based on the PCA scores of each in- equation was applied. We suggest that this was be- dividual along the first principal component (PC1) cause these represented the Scandinavian cinclus, axis. Data from Scandinavia and South-Eastern which are bigger and heavier than other European andNorthernPolandwereusedinthisanalysis. dippers. In these cases, sex could be verified by North Polish individuals with PC1 scores falling comparing measurements of their mates — males within the PC1 scores of the Carpathian individu- are consistently bigger than females — and by ob- als were considered as representing aquaticus,and serving the behavior of individuals within their a respective protocol was applied for cinclus. breeding territories; all these birds indeed ap- North Polish individuals with PC1 scores falling peared to be females. We calculated the repeatabil- between the aquaticus and cinclus scores were ity of measurements (intra-class correlation coef- considered as representing an intermediate pheno- ficients derived from ANOVA)following Lessels type. and Boag (1987), using data on White-throated Dippers captured during winters of 1991/1992 and 2005/2006 in Northern Poland. These individuals 3. Results were measured 2–10 (mean 3.3 ± 1.6 SD)times. 3.1. Phenotypic divergence between aquaticus and cinclus 2.1. Statistical analysis All measurements were highly repeatable (Table To classify phenotypes of dippers breeding in 1). Carpathian individuals were smaller than Scan- Northern Poland, we performed standardized dinavian ones in most measurements, and patterns Sikora & Neubauer: White-throated Dipper interbreeding in Poland 77

Table 2. Measurements of White-throated Dippers from the Carpathians (aquaticus), Northern Poland, and Scandinavia (cinclus). Mean values±1SD(all in mm).

Males Females

Measure- Carpathians N Poland Scandinavia Carpathians N Poland Scandinavia ment n =11 n =16 n =28 n =16 n =18 n =21

Wing length 95.5 ± 1.6 97.8 ± 1.6 98.4 ± 1.6 87.5 ± 1.5 89.9 ± 1.6 90.2 ± 1.3 Tarsus length 29.6 ± 0.6 30.0 ± 0.9 29.8 ± 0.8 27.7 ± 0.6 27.9 ± 1.0 28.3 ± 0.6 Head length 46.7 ± 0.8 47.2 ± 0.6 47.2 ± 0.7 45.0 ± 0.7 45.5 ± 0.6 45.9 ± 0.6 Bill length 16.4 ± 0.4 16.3 ± 0.4 16.3 ± 0.5 15.6 ± 0.4 15.5 ± 0.6 15.4 ± 0.5 Bill: from tip to nostrils 15.3 ± 0.6 15.5 ± 0.5 15.7 ± 0.5 14.9 ± 0.6 14.8 ± 0.5 14.9 ± 0.5 Bill depth 4.9 ± 0.2 4.8 ± 0.2 4.8 ± 0.2 4.6 ± 0.2 4.5 ± 0.2 4.5 ± 0.2 PC1 score 1.560 ± 0.194 0.020 ± 0.967 –0.649 ± 0.309 1.331 ± 0.388 –0.429 ± 0.639 –0.647 ± 0.467 PC2 score –0.259 ± 1.095 –0.069 ± 1.053 0.082 ± 0.940 0.220 ± 0.959 –0.285 ± 1.141 0.076 ± 0.886

Table 3. Coloration of breast, head and legs of White-throated Dippers from the Carpathians (aquaticus), Northern Poland, and Scandinavia (cinclus). Breast = the amount of reddish-brown feathers on the breast; Head = color of head with hind neck; Legs = leg color (all in percentages).

Males Females

Feature Carpathians N Poland Scandinavia Carpathians N Poland Scandinavia n =11 n =16 n =28 n =16 n =18 n =21

Breast More than 60% 100.0 33.3 0 87.5 11.1 14.3 31–60% 0 20.1 10.3 12.5 16.7 14.3 1–30% 0 13.3 41.4 0 38.9 47.6 0% 0 33.3 48.3 0 33.3 23.8 Head Brown 100.0 26.7 0 100.0 15.8 4.8 Intermediate 0 0.0 0 0 10.5 4.8 Dark brown 0 73.3 100.0 0 73.7 90.4 Legs Pale 81.8 26.7 0 81.2 5.6 4.8 Intermediate 18.2 0 0 18.8 5.6 0 Dark 0 73.3 100.0 0 88.8 95.2 of morphological divergence were similar in fore, the sexes were pooled in subsequent compar- males and females (Table 2). Carpathian birds also isons. The scores of Carpathian and Scandinavian tended to have paler legs, more reddish breast col- individuals did not overlap along PC1 axis (sexes oration, and paler head and hind neck (Table 3). pooled, PC1: t = 23.63, P < 0.0001; Fig. 2), (74) PCA was initially performed separately for males mainly due to the high contribution of color-based and females, but the sexes did not differ in PC traits and wing length to PC1 (Table 4). The scores scores within any population (Scandinavia, PC1: along PC2 were similar between Carpathian and t = 0.02, P = 0.98, PC2: t = –0.02, P = 0.98; Scandinavian individuals (t = –0.24, P = 0.81, (47) (47) (74) Northern Poland, PC1: t = –1.60, P = 0.12, PC2: Table 2). The first two axes explained 64.9% and (32) t = –0.56, P = 0.58; Carpathians, PC1: t = 66.2% of the total variance in males and in fe- (32) (25) –1.79, P = 0.09, PC2: t = 1.20, P = 0.24). There- males, respectively (Table 4). (25) 78 ORNIS FENNICA Vol. 85, 2008

Table 4. Results of a standardized principal compo- least occasionally breed far from its regular breed- nent analysis on morphological data of 112 adult ing range. White-throated Dippers from the Carpathians (aquaticus), Northern Poland, and Scandinavia (cinclus). 3.3. Distribution, composition PC1 PC2 and breeding success in Northern Poland

Males Females Males Females Between 1990 and 2006, we recorded 25 con- firmed and four probable breeding attempts of 23 Eigenvalues 3.49 3.61 2.35 2.35 pairs of White-throated Dippers in Northern Po- Variance land. The probable breeders represent pairs dis- explained (%) 38.82 40.13 26.06 26.08 Component loadings playing or building a nest early in the season but – wing length –0.72 –0.81 –0.11 0.08 without the breeding confirmed later on. All but – bill length 0.26 0.06 0.79 0.68 two breeding cases were recorded on six sites in – bill: from tip the western (Pomeranian)part of the North Polish to nostrils –0.21 –0.10 0.88 0.88 study area on the rivers S³upia (54°14’N, – bill depth 0.44 0.35 0.21 0.24 17°45’E), Bielska Struga (53°39’N, 17°59’E), – head length –0.28 –0.61 0.86 0.72 – tarsus length 0.01 –0.43 0.35 0.56 Bolszewka (54°35’N, 18°08’E), Radunia – breast color 0.89 0.78 0.13 0.31 (54°16’N, 18°30’E), £eba (54°32’N, 18°01’E) – head color 0.96 0.92 –0.05 0.22 and Skotawa (54°22’N, 17°10’E). In the Masurian – leg color 0.94 0.90 –0.02 0.28 Lakeland, single pairs bred on the Marózka (53°29’N, 20°22’E)and Symsarna (54°07’N, 20°35’E)rivers (Fig. 1). 3.2. Phenotypic composition Of 34 individual birds, four males and two fe- of the North Polish population males paired more than once. For example, the Swiss-ringed aquaticus male bred with three dif- PC1 scores for the White-throated Dippers breed- ferent females during five successive breeding ing in Northern Poland fell within the range of seasons in Northern Poland: with a ringed (Swed- cinclus in 76% of the cases for males and in 89% ish) cinclus female in 1994–95, with another for females, whereas those with PC scores sug- cinclus-like female in 1996 and with an aquaticus- gesting aquaticus were less numerous (24% of like female in 1997–98. Because five individual males and 11% of females). No intermediate indi- pairs bred in more than one year, and to avoid viduals were recorded among breeding adults, but pseudo-replication, these were incorporated into two male offspring of a phenotypically mixed pair analysis once only. Therefore, we trapped or iden- were intermediate; their PC1 scores fell between tified both partners for 23 pairs in total, including the range of Carpathian and Scandinavian birds four probable breeding cases. Most frequently, (Fig. 2). both mates had cinclus phenotype (65%; 15 pairs), Two ringing recoveries confirmed that White- whereas mixed pairs with mates showing different throated Dippers originating from Scandinavia phenotypes constituted about one-third (30%; 7 have bred in Northern Poland (Fig. 1). Addition- cases), all with males of aquaticus and females of ally, an individual with cinclus phenotype, ringed cinclus phenotype. Interbreeding between aquati- as a nestling in Northern Poland, had been subse- cus and cinclus in Northern Poland was further quently recorded breeding in central Sweden, confirmed by ringing recoveries: the above-men- showing that natal dispersal between Scandinavia tioned Swiss male and a ringed Swedish female and Northern Poland occurs in both directions. A bred in 1994 and in 1995. In a single case, both recovery from an aquaticus ringed as a nestling in birds represented aquaticus phenotypes, and in an the Alps (near Zurich, Northern Switzerland, additional case an aquaticus-phenotype female 47°17’N, 08°32’E; Fig. 1)and recorded breeding bred with an unknown partner. in Northern Poland (Hegelbach & Koch 1994, Most breeding attempts of White-throated Sikora 1994)indicates that this subspecies may at Dippers in Northern Poland were successful. Sikora & Neubauer: White-throated Dipper interbreeding in Poland 79

nests. Similarly, among ten breeding attempts of phenotypically mixed pairs, nine attempts were studied, and six of these proved successful. In 2004, a phenotypically mixed pair successfully raised two broods: fledglings were observed near nest on 30th April, and two nestlings were found in thesameneston29th May. Two unsuccessful broods of mixed pairs contained non-fertilized eggs; one mixed pair failed to produce young for an unknown reason. Two broods of the same pair of aquaticus phenotype were successful in both years with 4 and 6 young raised, respectively. Al- though the sample size is limited by the small po- pulation size, the data seem to indicate that no ap- parent reproductive barrier exists between the sub- species of White-throated Dipper in Northern Po- land.

4. Discussion

We showed that the White-throated Dipper popu- lation breeding in Northern Poland involves two subspecies that were previously thought to be re- productively isolated. However, cinclus and aquaticus also co-occur in the Cantabrian Moun- tains and Western Pyrenees (Campos et al. 2005a). Further studies are necessary to evaluate whether aquaticus and cinclus interbreed regularly in some parts of their breeding ranges, or whether the situa- tion in Northern Poland is unique. As could be ex- pected by their migratory habits, the out-of-range population in Northern Poland was established predominantly by cinclus individuals that had re- mained within their regular winter range and by aquaticus individuals that had dispersed unusually far from the Central European mountain ranges. Fig. 2. The frequency distribution of PC1 scores These two subspecies occasionally form mixed from principal component analysis based on nine morphological traits measured in 112 White- pairs in Northern Poland, although most pairs in throated Dippers from Carpathians, Scandinavia that area represent pure cinclus. Thereareafew and Northern Poland (sexes pooled). The arrows confirmed and probable breeding records from the show PC1 scores of two male White-throated Dip- German Lowland, but it remains unknown to pers that are offspring of a phenotypically mixed which subspecies these breeding birds belong pair from Northern Poland. (Creutz 1986, Bink 1992, Nicolai 1993). Compared to aquaticus, Scandinavian cinclus Among 12 broods of pairs with both mates repre- is more likely to breed far from its regular breeding senting cinclus phenotype (breeding in successive range due to its migratory habits. Movements of seasons included), ten attempts were followed by Scandinavian cinclus, documented by ringing re- us and eight were successful, indicated by re- coveries, reach 1,000 km (Andersson & Wester corded nestlings or recently fledged young near 1976). Such distances exceed the distance be- 80 ORNIS FENNICA Vol. 85, 2008 tween the breeding ranges of cinclus and aquati- ters may not help much in identification of such cus. For example, less than 500 km separates the subspecific hybrids. Thus, their “genetic history” breeding range of the Norwegian cinclus popula- will remain undiscovered unless molecular mark- tion and that of aquaticus in Germany (e.g., Harz ers are used to assign individuals. Mountains). Similarly, the breeding range of The situation in Northern Poland suggests that Southern Swedish cinclus and Southern Polish gene flow between subpopulations and subspecies (Sudetes) aquaticus are separated by 500–600 km. may not necessarily be a rare phenomenon, even if Thus, we suggest that a few cinclus may at least subspecies are separated by a geographical barrier. occasionally migrate to and breed within Central Gene flow may occur even if the population is European populations of aquaticus. More surpris- fragmented and/or some subpopulations show ingly, the 1,055-km long movement of aquaticus sedentary habits. The documented exchange of in- from Switzerland shows that northward natal dis- dividuals partially explains the high morphologi- persal from Central Europe does happen (Sikora cal variability reported in Central European dipper 1994). populations, and the low genetic differentiation Our results showed that color-based traits between subspecies. readily separate the two subspecies (Fig. 2). Scan- dinavian cinclus shows considerable variation in Acknowledgements. We thank Marcin Dziedzic and coloration of breast feathers, with a minority of Witold Michalczyk for assistance in trapping dippers in birds being similar to Carpathian aquaticus in this the Beskid Niski Mountains, and Marek Jêdra for organiz- ing accommodations. We also thank Zenek Rohde for pre- respect (Table 3). This finding indicates that the paring the map and two anonymous referees for their help- breast color alone, traditionally believed to be di- ful comments. agnostic and used to separate subspecies in some studies (e.g., Campos et al. 2005a), may not be suf- ficient to distinguish between subspecies. Further- Skandinavian ja Keski-Euroopan koski- more, White-throated Dipper shows extensive karojen Cinclus cinclus alalajit pesivät within-population variation in plumage color- sekapareina eristyneessä populaatiossa ation, influenced by habitat, sex and age (Balat Pohjois-Puolassa 1961, Spitznagel 1995a, b). With these facts in mind, a special caution is necessary during assign- Skandinaviassa ja Keski-Euroopassa pesivien ment of individual birds. Therefore, although sep- koskikaran (Cinclus cinclus) cinclus-jaaquati- aration of subspecies in our sample was clear, we cus-fenotyypit ovat asumattoman alavan maan toi- recommend to use the term “phenotype” instead of sistaan eristämiä. Pohjois-Puolassa todettiin “subspecies”. However, it seems extremely un- 1990–2006 kaikkiaan 23 koskikaraparilla 25 var- likely, that the observed distribution of pheno- maa ja neljä todennäköistä pesintää. Valtaosa alu- types in the studied North Polish dipper population een koskikaroista edusti Skandinavian cinclus-fe- would not, at least partially, reflect the presence of notyyppiä (76 % koiraista ja 89 % naaraista), ja vä- two subspecies. Finally, the obtained ringing re- hemmistö muistutti Karpaattien seudun aquati- coveries undisputedly confirmed immigration and cus-yksilöitä (vastaavasti 24 ja 12 %). Fenotyyp- interbreeding between two subspecies of White- pisen sekaparin kaksi saman pesyeen koirasta oli throated Dipper. Such an exchange of individuals ulkoisesti välimuotoisia. between populations, with subsequent gene flow, Rengaslöytöjen avulla varmistui, että molem- may contribute to maintaining high color variabil- pia fenotyyppejä pesii Pohjois-Puolassa. Puhtaita ity in dipper populations and reduce their genetic cinclus-fenotyypin pareja oli 15, puhtaita aquati- differentiation (Lauga et al. 2005). cus-pareja yksi, ja fenotyyppien sekapareja (cin- The two male White-throated Dipper offspring clus x aquaticus)todettiin seitsemän. Valtaosa pe - of a subspecifically mixed pair appeared pheno- simäyrityksistä onnistui, eikä parin fenotyyppi- typically different. One was similar to its mother koostumus näyttänyt vaikuttavan asiaan. Yksi (cinclus phenotype), whereas the other was remi- Puolassa syntynyt yksilö löytyi myöhemmin pesi- niscent of its father (aquaticus phenotype). vänä Ruotsista. Päälevinneisyysalueen ulkopuoli- Clearly, the use of multiple morphological charac- set – kuten tutkittu puolalainen – populaatiot, joi- Sikora & Neubauer: White-throated Dipper interbreeding in Poland 81 hin liittyy allopatristen alueiden yksilöitä, voivat Kondracki, J. 2002: Geografia regionalna Polski. — toimia siltana ja ylläpitää geneettistä vaihtelua se- PWN, Warszawa (In Polish) kä tässä tutkimuksessa raportoitua vähäistä ge- Lauga, B., Cagnon, C., D’Amico, F., Karama, S. & Mou- chès, C. 2005: Phylogeography of the White-throated neettistä eriytymistä alalajien välillä. Dipper Cinclus cinclus in Europe. — Journal of Ornit- hology 146: 257–262. Lehikoinen, E. & Hakala, J. 1988: Variation in weight of References migratory Dippers Cinclus cinclus in their Finnish winter quarters. — Bird Study 35: 101–108. 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Bub, H. 1984: Kennzeichen und Mauser Europäischer Schmid, W. & Spitznagel, A. 1985: The Sexual Size Di- Singvögel, 3. Teil. Seidenschwanz, Wasseramsel, morphism of South-German Dippers (Cinclus c. aqu- Zaunkönig, Braunellen, Spötter, Laubsänger, Gold- aticus): Biometrics, Function and Possible Causes. — hähnchen (Bombycillidae, Cinclidae, Troglodytidae, Ecology of Birds 7: 349–408. (In German with Eng- Prunellidae, Sylviidae I). Ziemsen, Wittenberg. (In lish summary) German) Siegel, S. & Castellan, N.J. 1988: Nonparametric Statistics von Burg, G. 1924: Die Schweizerischen Wasseramseln. for the Behavioural Sciences. 2nd ed. — McGraw- — Der Weidmann 6: 7–10. (In German) Hill, New York. Campos, F., Gutiérrez-Corchero, F., Hernández, M.A., Sikora, A. 1993: Occurrence of Scandinavian subspecies Rivas, J.M. & López-Fidalgo, J. 2005a: Biometric dif- of the Dipper (Cinclus cinclus cinclus)in Poland. — ferences among the Dipper Cinclus cinclus popula- Notatki Ornitologiczne 34: 213–230. (In Polish with tions of Spain. — Acta Ornithologica 40: 87–93. English summary) Campos, F., Gutiérrez-Corchero, F., López-Fidalgo, J., & Sikora, A. 1994: A long-distance passage of the central Hernández, M. A. 2005b: A new criteria to sex Euro- European Dipper subspecies (Cinclus c. aquaticus) pean Dippers Cinclus cinclus in the Iberian Peninsula. and its cross-breeding with the Scandinavian subspe- — Revista Catalana d’Ornitologia 21: 43–46. cies (C. c. cinclus)in the north of Poland. — Notatki Cramp, S. 1988: The Birds of the Western Palearctic. 5. — Ornitologiczne 35: 182–185. (In Polish with English Oxford University Press, Oxford. summary) Creutz, G. 1986: Die Wasseramsel. — Ziemsen, Witten- Sokal, R.R. & Rohlf, F.J. 1995: Biometry. — Freeman, berg. (In German) New York. Esteban, L., Campos, F. & Ariño, A.H. 2000: Biometrics Spitznagel, A. 1995a: Die Farbvariabilität der Wasseram- amongst Dippers Cinclus cinclus in the north of Spain. sel (Cinclus cinclus)und der Einfluß ökologischer und — Ringing and Migration 20: 9–14. ethologischer Faktoren. — Acta Ornithoecologica 3: Glutz von Blotzheim, U.N. & Bauer, K.M. 1985: Hand- 167–189. (In German) buch der Vögel Mitteleuropas, vol. 10/II. — Aula, Wi- Spitznagel, A. 1995b: Beziehungen zwischen Ektoparasi- esbaden. (In German) ten und der Farbvariabliltät der Wasseramsel (Cinclus Greenway, J.C. & Vaurie, C. 1958: Remarks on some cinclus). — Acta Ornithoecologica 3: 199–212. (In forms of Cinclus (Aves). — Breviora 89: 1–10. German) Hagemeijer, E.J.M. & Blair, M.J. (eds.)1997: The EBCC Svensson, L. 1992: Identification guide to European Pas- Atlas of European Breeding Birds: Their Distribution serines. 4th ed. Stockholm. and Abundance. — Poyser, London. Tyler, S.J. & Ormerod, S. 1994: The Dippers. — Poyser, Hegelbach, J., & Koch, B. 1994: A male Dipper Cinclus London. cinclus aquaticus, ringed as nestling in Switzerland, Vuorinen, J. & Tyrberg, T. 1994: Strömstarens teoretiska migrated 1,055 km and bred in Poland with a Swedish vårflyttningskapacitet. — Cinclus Scandinavicus 7: female Dipper C. c. cinclus. — Ornitologische Beo- 4–9. (In Swedish) bachter 91: 295–299. (In German with English sum- Zink, G. 1981: Der Zug Europäischer Singvögel. — Vo- mary) gelzug-Verlag, Möggingen. (In German)